How to create a rough green emerald material in Cycles
Maybe this will help get you started.  You will still have a lot of work to do in order to refine the materials and lighting to get this to work.



Here's a link to the Fracture Modifier branch which was used to break up a model. https://www.dropbox.com/sh/xiuirkoo0rac5tw/AAB2XQbs9K5uTIYcbDPUDW1Ca